The present invention relates to a process that accurately, quickly and inexpensively modifies a standard printed circuit board in order to change the board""s function. More particularly, a standard printed circuit board used in an electronic trip unit is automatically altered to change the board""s function, offering an electronic trip unit having different options.
The electronics industry has expanded dramatically over the last several decades. Each year, new electronic products are introduced and previously existing products are improved. Virtually every one of these electronic products includes a printed circuit.
The requirements placed on printed circuit capabilities have increased greatly in conjunction with the constant demand for improved electronics technology. Multilayer printed circuits have literally thousands of circuitry traces. Additionally, as electronic products continue to become smaller in size, the printed circuit associated with the individual product must also decrease in size, resulting in tighter manufacturing tolerances.
There are numerous methods for manufacturing a printed circuit board, the present invention is suitable for use with any printed circuit board regardless of the manufacturing process used to produce the circuit board.
Individual printed circuit boards may be assembled to form a multilayer printed circuit board constructed by stacking a predetermined number of boards one atop another. In such a construction a cured or semi-cured polymetric non-conductive material is in contact with the copper surface of the adjacent printed circuit board. The stacked circuit board assembly may be laminated together by application of heat and pressure to form a multilayer printed circuit board.
To remain competitive, printed circuit manufacturers must keep fabrication costs as low as possible. This is an extremely difficult task, given that printed circuit manufacturing entails a number of independent processing steps. Each printed circuit board is designed and formed to serve a specific function. It is often desirable to minimally change a printed circuit to effectuate an option of the electronic product. When it is desirous to modify the function of the printed circuit board, for example, to accommodate different options for the printed circuit board, a jumper wire is often utilized. This is accomplished by adding or subtracting jumpers in an effort to alter the circuit pattern. Jumpers consist of electrical wires that are soldered in place, or if already in place then removed with cutters.
When using a multi-layer printed circuit board, several layers are laminated together so that joining electrical traces on different layers is accomplished by a lands which extends through the respective layers with a plated through hole. The leads of various components are made to penetrate through the through holes of the respective lands and are soldered to complete the electrical connection. To modify the circuit, a direct connection between two points is accomplished by soldering the jumper wire between these two points, which differs from the electrical connection made by the original wiring pattern on the substrate. This method is preformed manually so it is error prone and expensive.
There are other methods of altering the circuit patterns, such as using small dual inline package (dip) switches, which can be set and reset. Again, this is a manual operation that is error prone and expensive. Another alternative is to add integrated circuit memories that can be programmed with information that changes the circuit function. Although automatic, the use of programmable components is expensive and extra components reduce product reliability.
Due to ongoing requirements for automated processes in the manufacturing of printed circuit boards to eliminate error and the always present need to minimize cost, it is desirable to provide an assembly process that automatically and inexpensively removes electrical traces on a standard printed circuit board in order to change the board""s function. The present invention provides an automated manufacturing process that takes a standard printed circuit board and removes pre-determined electrical traces to change the function of the standard printed circuit board. By removing the predetermined electrical traces, one can accurately and inexpensively offer a printed circuit board with different options.
The removal of the electrical trace is accomplished by using a computer numerically controlled (CNC) milling machine, or similar equipment capable of obtaining like results. The CNC machine, comprising a work surface and a cutting element, is activated by a personal computer preloaded with a software program designed to recognize an inputted catalog number and respond by milling the designated area on the circuit board. To utilize the process, an operator loads and secures the printed circuit board onto the work surface. The operator then inputs the catalog number, which defines the printed circuit board having the desired option, after loading the printed circuit board the automated milling process, begins and the targeted electrical traces are removed by the milling process. Upon conclusion the operator removes a modified printed circuit board from the machine.
The CNC milling machine with the cutting element in place is capable of accurately removing a copper trace without touching any adjacent traces on the same layer or touching traces on subjacent layers.